Find direct, verified answers to the most common questions regarding FIEZEL's learning platform, CEFR curriculum, offline PWA features, and adaptive technology.
FIEZEL is an independent, free, adaptive English learning progressive web application designed to help learners practice English through grammar, vocabulary, reading, speaking, and listening activities organized around CEFR proficiency levels (A1 to C2).
Unlike traditional linear textbooks, FIEZEL adapts to each learner's answer patterns, scheduling spaced repetition for errors and dynamically adjusting exercise difficulty using its client-side Braincore engine.
FIEZEL provides high-volume, structured language practice with 180 grammar lessons (4,500 exercises), 2,440 vocabulary items with spaced repetition, 312 graded reading passages (1,560 questions), 1,400+ listening exercises, and 36 speaking sessions.
The platform delivers focused 25-exercise sessions with instant feedback and contextual error explanations in Indonesian and Thai.
FIEZEL was created and engineered by Fitra Rustqi (@fitrarustqi), an independent software developer and educational technologist.
The platform's source code, verified curriculum banks, and release quality gates are maintained transparently on GitHub at github.com/fiezel-apps/FIEZEL-APPS.
FIEZEL is spelled F-I-E-Z-E-L and pronounced /ˈfiːzəl/ ("Fee-zel").
It is an independent educational software product, completely distinct and unrelated to "diesel" (petroleum distillate fuel, diesel combustion engines, Rudolf Diesel, or the Italian fashion brand) or "fizzle" (to make a hissing sound or fail feebly).
Yes. FIEZEL is 100% free with no subscription, no in-app purchases, no locked content, and no advertisements.
All 180 lessons, question banks, reading texts, and adaptive features are accessible immediately without payment.
FIEZEL operates as an installable Progressive Web App (PWA) in any modern browser without requiring app store downloads.
Learners can take an initial 25-question diagnostic placement test or choose a CEFR level to practice 25-exercise focused sessions where the Braincore engine adapts content to their errors.
Yes. Once installed to your device home screen as a PWA, core grammar lessons, vocabulary drills, and reading passages function offline without an active internet connection.
Cloud AI conversational tutor responses and neural text-to-speech voice streaming require an active network connection.
FIEZEL provides practice across five core English skills: grammar, vocabulary, reading comprehension, listening, and speaking.
Each skill possesses a dedicated module with tailored feedback mechanisms and progress indicators.
Yes. FIEZEL features 180 grammar lessons with 25 exercises each (4,500 total questions) across CEFR A1 to C2, providing immediate explanations for why incorrect choices fail.
Curriculum coverage spans basic present tenses, past aspects, relative clauses, conditionals, modal verbs, and complex C1/C2 discourse structures.
Yes. FIEZEL includes 2,440 curated vocabulary entries taught through contextual sentences and adaptive spaced repetition.
Words return for review based on individual forgetting curves managed by the Braincore engine.
Yes. FIEZEL includes 312 graded reading passages and 1,560 comprehension questions spanning A1 beginner notices to C2 advanced essays.
Every question includes evidence citations directly tied to passage sentences to verify answers objectively.
Yes. FIEZEL provides over 1,400 listening exercises with multi-character audio scripts in IELTS and TOEFL exam styles.
Exercises replicate real exam rules: IELTS sections allow questions to be visible during playback, while TOEFL sections hide questions until audio completes.
Yes. FIEZEL provides 36 interactive speaking practice sessions using the browser SpeechRecognition API for real-time speech assessment.
Learners practice answering prompts aloud with instant acoustic and semantic feedback.
FIEZEL covers all six CEFR proficiency bands: A1 (Breakthrough), A2 (Waystage), B1 (Threshold), B2 (Vantage), C1 (Effective Operational Proficiency), and C2 (Mastery).
Learners can start at A1 as absolute beginners or take the 25-question placement diagnostic to skip ahead.
No. FIEZEL uses CEFR levels strictly as an internal pedagogical difficulty benchmark. FIEZEL is an independent software tool and does not confer official certificates or accredited qualifications (it is not an official testing body).
It is designed for personal skill development, self-study, and classroom assignment practice.
Braincore is FIEZEL's proprietary client-side cognitive engine. Instead of scoring linear quizzes with arbitrary percentages, Braincore implements Bayesian Knowledge Tracing (BKT) to separate genuine concept mastery from lucky guesses, diagnoses grammatical errors via a fine-grained Misconception Ledger, and calculates dynamic Spaced Repetition decay directly in your browser.
Braincore runs 100% locally on the student's device with zero server latency, offline readiness, and complete privacy by design. In classroom settings, it powers KelasKu's automated skill heatmaps.
No account or registration is required. FIEZEL stores learning progress locally on your device via browser storage, ensuring complete privacy without requiring an email or phone number.
Clearing browser storage will reset local progress; optional class join codes connect students to teachers without sharing private identifiers.
FIEZEL runs on Android, iOS, Windows, macOS, and Linux through any modern web browser (Chrome, Safari, Edge, Firefox). It can be added to the home screen as a full-screen Progressive Web App.
On Android, install via Chrome's menu (⋮) → "Install app". On iOS, install via Safari's Share button → "Add to Home Screen".
Yes. FIEZEL includes a Japanese course covering JLPT N5–N4 grammar (422 points across 27 families), vocabulary (1,884 items), reading (150 passages), and writing (54 prompts). Listening and speaking are currently English-only.
Japanese listening and speaking modules are deliberately hidden until Japanese neural audio pipelines are ready.
KelasKu is a built-in teacher layer within FIEZEL that enables educators to create classes via 6-character room codes, assign curriculum-aligned tasks, and view learning analytics for up to 250 students.
KelasKu is configured for single classroom pilots (~30 students) and is not intended for whole-school administrative deployments. Learn more on the KelasKu for Teachers page.
Open fiezel.my.id/app/ in any web browser on your phone, tablet, or computer. You can start practicing immediately or take the placement test without signing up.
No downloads from app stores are required, and all learning materials are available on day one.
Jump straight into practice. No account required, completely free.